Please set the record straight! Thermostat settings for 2 story house

Even HVAC companies are all over the place on how the thermostat should be set in a two story house in the summer versus the winter. Below are the first four HVAC company comments that came up in Google. Please let me know how my two thermostats should be set in summer and winter. Thanks!

It seems like setting the downstairs 2 degrees warmer in the summer would overwork the upstairs unit.

​

In the summer:

1. Set the lower floor 2 degrees cooler

https://metalmasters-inc.com/how-to-effectively-set-your-thermostat-for-a-multi-story-home/

1. Set the lower floor 2 degrees cooler

https://www.mastermechanical.net/how-set-your-thermostat-multi-story-home

1. Set the lower floor 2 degrees warmer

https://www.donmarcompany.com/about-us/blog/2018/june/how-to-set-your-thermostat-in-a-multi-story-home/#:~:text=During%20the%20summer%2C%20set%20your,and%20upstairs%20two%20degrees%20colder.

1. Set the lower floor 2 degrees warmer

https://bardi.com/how-to-effectively-set-your-thermostat-for-a-multi-story-home/

​

Edit: readability